The present invention relates a deflection system with quadripolar correction coils for use with a cathode ray tube and more particularly to a quadripolar correction coil configuration which is easily manageable in terms of deflection system design and yet allows for mechanical assembly of a split ring magnetic core, on which toroidal-type vertical deflection coils are mounted, around saddle-type horizontal deflection coils.
In conventional black and white television receivers, horizontal and vertical deflection coils are energized to bend the electron beam in a cathode ray tube causing the beam to scan across the entire face of the cathode ray tube in the horizontal and vertical directions.
Deflection coils traditionally comprise a pair of either toroidal or saddle-shaped coils mounted on an annular or ring-shaped ferromagnetic core. Toroidal coils can be wound directly on a solid ring magnetic core but the current state of technology requires that commercially acceptable saddle coils be pre-wound and thereafter mounted on the core. Since the flared ends of a saddle coil exceed the inner diameter of the core, the core must be split into at least two separate pieces and then reassembled around the pre-wound saddle windings. A core broken in such a manner is referred to as a split ring magnetic core.
Horizontal and vertical deflection coils may be all toroidal, all saddle, or one set toroidal and one set saddle. However, the power consumed by deflection coils is dependent both on the type of coil and the frequency at which the coil is operated. It is generally recognized in the television industry that in a horizontal deflection circuit which operates at a high frequency such as the 15,750 cycle per second frequency used in United States commercial television, less energy is consumed driving saddle horizontal deflection coils than is needed to drive toroidal horizontal deflection coils. Further, it is generally recognized that in a high impedance vertical deflection circuit which operates at a low frequency such as the 60 cycle per second frequency used in the United States, less energy is consumed driving toroidal vertical deflection coils than is needed to drive saddle vertical deflection coils.
Accordingly, the deflection system which offers minimum power consumption is one which uses deflection coils in a hybrid arrangement with the higher frequency horizontal coils of a saddle-type and the lower frequency vertical coils of a toroidal-type.
When using such a hybrid system, the magnetic core is split at the vacant areas which occur along the horizontal axis of the core between the toroidal vertical coils to allow assembly of the core around the pre-wound saddle-type horizontal coils.
Conventional color television receivers employ plural beam cathode ray tubes either in a triad or an in-line arrangement. The plural electron beams are deflected in a similar manner as single electron beams, but additional corrective coils may be required or desired to assure proper convergence of the plural beams at the point of impact on the face of the tube. As evidenced by British Pat. No. 1,323,154 to Philips Electronic and Associated Industries, Ltd., published July 11, 1973, quadripolar correction coils are known to provide a means of assuring proper convergence in plural beam tubes.
Quadripolar correction coils in an in-line system usually comprise four individual coils mounted on the magnetic core to establish alternate north and south poles along the diagonals of the deflection system. Typically, the quadripolar coils are toroidal in form because saddle quadripolar coils result in mounting and alignment requirements which are extremely complex and in a coil size which is so bulky as to require an unreasonably large core. Instead, toroidal quadripolar coils have been used with saddle horizontal and saddle vertical deflection coils. To produce the alternate north and south poles along the diagonals of the deflection system, the toroidal quadripolar coils are centered along the horizontal and vertical axes of the system. In such cases, the necessary break in the core to allow for assembly of the core around the saddle-shaped horizontal and vertical deflection coils can be located anywhere between adjoining quadripolar coils.
An apparently insurmountable fabrication problem arises, however, in the use of toroidal-type quadripolar coils with the more efficient deflection system comprising saddle-type horizontal coils and toroidal-type vertical coils. To establish alternate north and south poles along the diagonals of the deflection system, conventional toroidal quadripolar coils are located along the horizontal axis of the system, but these quadripolar coils then overlie the horizontal axis separation on the core between the toroidal vertical deflection coils and thereby eliminate any vacant areas at which the core can be split to allow assembly of the core around the pre-wound saddle-type horizontal coils.
Movement of the quadripolar coils or windings of the coils away from the horizontal axis based solely on the need to allow for splitting and reassembly of the core results in an unsatisfactory quadripolar magnetic correction field.
Specifically, the shape of the required quadripolar magnetic correction field is dependent on a number of factors including the shape of the horizontal and vertical deflection fields, the shape of the cathode ray tube and the waveform of excitation signals used to generate the quadripolar, horizontal and vertical fields. The interrelationship of these factors is extremely intricate and a change in one requires reanalysis and redesign of the entire system. Accordingly, redesign of the quadripolar coils based only on the need to provide enough vacant area on the core to allow assembly of the core around the saddle horizontal coils results in a quadripolar correction field which requires reanalysis and redesign of the entire deflection system. This can be a costly and, for some changes in the quadripolar coil configuration, nearly impossible task.
It is accordingly an object of the present invention to provide a low energy consuming deflection system with toroidal quadripolar deflection coils.
It is another object of the present invention to provide a hybrid deflection system with quadripolar correction coils, the quadripolar correction coils having a configuration which provides a satisfactory quadripolar correction field and yet allows for assembly of a split ring magnetic core around saddle-type deflection windings.
It is a further object of the present invention to provide toroidal-type quadripolar correction coils which are readily compatible for use with saddle-type horizontal deflection coils and torroidal-type vertical deflection coils.